The field of the present invention is a liquid cooling system for liquid cooled motorcycle engines and particularly those having a front leg shield, a step floor and the engine mounted behind the step floor.
Motorcycles and particularly smaller motorcycles such as motor scooters have typically employed air-cooled engines. Air-cooled engines are lighter in weight and require less space than liquid-cooled systems often referred to as water-cooled systems. With liquid cooling, a radiator is required along with a water jacket on the engine and tubing connecting the two. These features add both weight and require additional space. Cooling fluid also adds weight to the system. Furthermore, the radiator must be located in an area of the vehicle experiencing air flow during forward motion. Consequently, special ducting and additional space may be needed to realize proper radiator efficiency.
On smaller motorcycles, compact design is important to aesthetic appearance as well as low wind resistance, reduction in weight and space allocation for the components. Weight and weight distribution of components is also important for performance, efficiency and handling. In smaller motorcycles, added components can effect weight distribution and overall weight disproportionately because of an initial low weight.
In motorcycles and particularly smaller motorcycles such as motor scooters, an arrangement employing a front leg shield, a step floor rearwardly of the front leg shield and an engine driving the rear wheel from a location behind the step floor has been common. One location for the radiator of a liquid cooling system for a motorcycle of this design is at the front leg shield. In such a system, the feed and return lines of the cooling system may extend beneath the step floor. This location dictates that the top of the cooling jacket on the engine is above the lowermost portion of the feed and return lines. Consequently, air may become trapped in the water jacket as any path returning it to the radiator must extend downwardly from the water jacket. The size of the required return line for adequate cooling efficiency and the need to periodically terminate flow below certain cooling temperatures make it difficult to quickly and appropriately discharge the air from the cooling jacket.